Corsair Professional AX760i / AX860i PSU review: extremely efficient

With prices of £158 and £166 respectively, the Corsair AX760i and AX860i are more expensive than the power supplies from our recent round-up, but you do get high-quality PSUs for that price. Their efficiency is outstanding, they're extremely quiet and the voltages are super-stable.

These two power supplies are extremely efficient and employ a digital controller

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With prices of £158 and £166 respectively, the Corsair AX760i and AX860i are more expensive than the power supplies from our recent round-up, but you do get high-quality PSUs for that price. Their efficiency is outstanding, they're extremely quiet and the voltages are super-stable. See all components buying advice.

In early August we reviewed the Corsair AX1200i, the first power supply for high-end desktop PCs to use a digital controller, and gave it the Gold Award. It proved to be extremely efficient, very silent with very low ripple values, plus you can control the PSU entirely via Corsair link. Finally we saw some innovation in the world of computer power supplies.

Since then Corsair released lower-capacity models built with the same technology. Hardware.Info tested the 760-watt AX760i and 860-watt AX860i.

Traditional power supplies have analogue components for regulating the voltages in order to keep the efficiency as high as possible. Corsair is the first to implement a DSP (digital signal processor) in a desktop PC power supply. Corsairs claims a DSP is faster and more accurate, which should results in extremely low ripple values. The manufacturer promises ripple values less than a third of the maximum ATX specifications (40 mVtt instead of 120 mVtt).

ATX specs also indicate that voltages can deviate by a maximum of 5 percent, but Corsair has lowered that to 1.5 percent. Stable voltages makes a PC run more stable as well. The faster and more accurate working of the DSP along with the absence of various analogue components also lower the amount of energy consumed by the PSU itself. The AX1200i is 80 Plus Platinum certified, but Corsair claims that the power supply is more efficient than (almost) any existing 80 Plus Platinum models. We will put that claim to the test.

A unique feature of the Corsair AX-i power supplies is the ability to connect the PSU to the Corsair Link system. With an included module you can connect the Corsair AX760i, AX860i and AX1200i to an internal USB 2.0 port on the motherboard. The Corsair Link software then lets you monitor various components of the power supply, including the voltage on the different rails, the energy consumption of each cable, the total usage, the efficiency, the temperature, the fan speed, and so on.

The fan speed can also be regulated with the software. You can create a profile for the fan, based on the temperatures of the PSU, the CPU, the graphics card and other variables. If you have Corsair water cooling or Corsair Dominator RAM modules, you can control those as well with the same software. Under light loads the measurements of usage and efficiency are not always 100 percent accurate, something Corsair also mentions. The software makes it possible to supply the max amperes on one or more plugs, if needed. This is great for extreme overclockers that like to boost their CPU and/or GPU.

The Corsair AX760i and AX860i both have a single 12V rail. In the AX760i it can supply 63.3 ampere, in the AX860i that's 71.6 ampere. That means that both PSUs are able to supply their entire maximum capacity entirely on 12V. Both models have the same number of connectors: 8x molex, 12x SATA and 6x 6/8-pin PEG. The PSUs are entirely modular, and all of the cables are sleeved. They both have a 12 cm fan, that is inactive until they reach 30 percent of their capacity. These are semi-passive PSUs, in other words. A USB cable is included for connecting them to Corsair Link.